Conventionally, various devices and methods have been proposed to correct acoustic characteristics in a vehicle interior. For example, first, in a listening environment such as inside the vehicle interior, a microphone is placed at a specific position such as a driver's seat, and frequency characteristics between the speaker and the microphone are measured. Then, the frequency setting, amplitude setting, and band setting of a filter are optimized in such a way as to be within an allowable range of a target response curve, thereby correcting the frequency characteristics. Such a method has been known (Refer to Patent Literature 1, for example).